Rec. ITU-R F.1397-2
1
RECOMMENDATION ITU-R F.1397-2*
Error performance objectives for real digital radio links used in
the international portion of a 27 500 km hypothetical
reference path at or above the primary rate
(Question ITU-R 210/9)
(1999-2001-2002)
The ITU Radiocommunication Assembly,
considering
a)
that the ITU-T has specified the error performance parameters and objectives for
international constant bit rate digital paths at or above the primary rate in ITU-T Recommendation G.826, and for international constant bit rate synchronous digital paths in ITU-T Recommendation G.828;
b)
that the ITU-T has specified the error performance events and the block structures for
synchronous digital hierarchy (SDH) multiplex and regenerator sections in ITU-T Recommendation G.829;
c)
that Recommendation ITU-R F.1491 provides the error performance objectives for real
digital radio links used in the national portion of a 27 500 km hypothetical reference path at or
above the primary rate;
d)
that any real path link for digital data transmission at or above the primary rate may be
realized using a linear and/or a redundant topology, depending on the needs of network providers;
e)
that there is a need to establish the performance objectives for real digital radio links in
order to allow a proper engineering of the radio links,
recommends
1
that for the error performance objectives (EPOs) applicable to each direction of any real
radio link of length Llink can be derived by means of equation (1) and using the values in Tables 1a
and 1b for SDH system design according to ITU-T Recommendation G.828 and values in Tables 2a
and 2b for system design according to ITU-T Recommendation G.826.
The lower limit of Llink, used to scale the objectives to the real case, is Lmin. Provisionally Lmin is
50 km.
EPO  Bj  (Llink / LR)  Cj
where:
j  1
for Lmin  Llink  1 000 km
for intermediate country
j  2
for 1 000 km < Llink
for intermediate country
j  3
for Lmin  Llink  500 km
for terminating country
j  4
for 500 km < Llink
for terminating country.
____________________
*
This Recommendation supersedes Recommendation ITU-R F.1092 that is been deleted.
(1)
2
Rec. ITU-R F.1397-2
EPO is substituted by the parameters errored second ratio (ESR), severely errored second ratio
(SESR) and background block error ratio (BBER) as appropriate.
LR is the reference length, LR  2 500 km
BR is a block allowance ratio, BR  (0 < BR  1);
TABLE 1a
Parameters for the EPO for intermediate countries according to
ITU-T Recommendation G.828
Parameter
Bit rate
(kbit/s)
Lmin  Llink  1 000 km
1 000 km < Llink
B1
C1
B2
C2
ESR
1 664
5  10–4 (1  BR)
0
5  104
2  10–4  BR
ESR
2 240
5  10–4 (1  BR)
0
5  104
2  104  BR
ESR
6 848
5  104 (1  BR)
0
5  104
2  104  BR
ESR
48 960
1  10–3 (1  BR)
0
1  103
4  104  BR
ESR
150 336
2  103 (1  BR)
0
2  103
8  104  BR
SESR
1 664-150 336
1  104 (1  BR)
0
1  104
4  105  BR
BBER
1 664-48 960
2.5  106 (1  BR)
0
2.5  106
1  106  BR
BBER
150 336
5  106 (1  BR)
0
5  10–6
2  106  BR
TABLE 1b
Parameters for the EPO for terminating countries according to
ITU-T Recommendation G.828
Parameter
Bit rate
(kbit/s)
Lmin  Llink  500 km
500 km < Llink
B3
C3
B4
C4
ESR
1 664
5  10–4 (1  BR)
0
5  10–4
1  10–4  BR
ESR
2 240
5  10–4 (1  BR)
0
5  10–4
1  10–4  BR
ESR
6 848
5  10–4 (1  BR)
0
5  10–4
1  10–4  BR
ESR
48 960
1  10–3 (1  BR)
0
1  10–3
2  10–4  BR
ESR
150 336
2  10–3 (1  BR)
0
2  10–3
4  10–4  BR
SESR
1 664-150 336
1  10–4 (1  BR)
0
1  10–4
2  10–5  BR
BBER
1 664-48 960
2.5  10–6 (1  BR)
0
2.5  10–6
5  10–7  BR
BBER
150 336
5  10–6 (1  BR)
0
5  10–6
1  10–6  BR
Rec. ITU-R F.1397-2
3
TABLE 2a
Parameters for the EPO for intermediate countries according to
ITU-T Recommendation G.826
Parameter
Bit rate
(Mbit/s)
Lmin  Llink  1 000 km
1 000 km < Llink
B1
C1
B2
C2
ESR
1.5-5
2  10–3 (1  BR)
0
2  10–3
8  10–4  BR
ESR
>5-15
2.5  10–3 (1  BR)
0
2.5  10–3
1  10–3  BR
ESR
>15-55
3.75  10–3 (1  BR)
0
3.75  10–3
1.5  10–3  BR
ESR
>55-160
8  10–3 (1  BR)
0
8  10–3
3.2  10–3  BR
ESR
>160-3 500
See Note 6
See Note 6
See Note 6
See Note 6
SESR
1.5-3 500
1  10–4 (1  BR)
0
1  10–4
4  10–5  BR
BBER
1.5-3 500
1  10–5 (1  BR)
0
1  10–5
4  10–6  BR
TABLE 2b
Parameters for the EPO for terminating countries according to
ITU-T Recommendation G.826
Parameter
Bit rate
(Mbit/s)
Lmin  Llink  500 km
500 km < Llink
B3
C3
B4
C4
ESR
1.5-5
2  10–3 (1  BR)
0
2  10–3
4  10–4  BR
ESR
>5-15
2.5  10–3 (1  BR)
0
2.5  10–3
5  10–4  BR
ESR
>15-55
3.75  10–3 (1  BR)
0
3.75  10–3
7.5  10–4  BR
ESR
>55-160
8  10–3 (1  BR)
0
8  10–3
1.6  10–3  BR
ESR
>160-3 500
See Note 6
See Note 6
See Note 6
See Note 6
SESR
1.5-3 500
1  10–4 (1  BR)
0
1  10–4
2  10–5  BR
BBER
1.5-3 500
1  10–5 (1  BR)
0
1  10–5
2  10–6  BR
2
that for the EPOs evaluation in recommends 1, the error performance parameters for any
real link are defined as follows:
–
ESR is the ratio of ES events to total seconds in the available time during a fixed
measurement interval;
–
SESR is the ratio of SES events to total seconds in the available time during a fixed
measurement interval;
–
BBER is the ratio of BBE events to total blocks in the available time during a fixed
measurement interval. The count of total blocks excludes all blocks during SES.
In Annex 1 some examples of application of the proposed method are shown.
In Annex 2 an example of real path, links and hops is shown.
In Annex 3 an example of the relationship between bit error ratio (BER) and errored blocks (EBs) is
shown.
4
Rec. ITU-R F.1397-2
NOTE 1 – The ES, SES and BBE events and the block structure for SDH multiplex and regenerator
sections are defined in ITU-T Recommendation G.829, the ES, SES and BBE events and the block
structure for paths are defined in ITU-T Recommendations G.826 and G.828.
NOTE 2 – A real link is defined as a portion of a path coming from partitioning and it is
characterized by its real length Llink.
NOTE 3 – The effects of interference and all other sources of performance degradations are
included in the values in Tables 1a and 1b.
NOTE 4 – The EPOs apply only when the system is considered to be available. The entry and exit
criteria into and from the unavailable state are defined in the relevant Recommendation (see ITU-T
Recommendation G.826).
NOTE 5 – According to ITU-T Recommendations G.826 and G.828 the suggested evaluation
period is one month for any parameter. In radio-relay links these objectives should be respected for
any month (see Recommendation ITU-R P.581).
NOTE 6 – The ESR objective for higher bit rate paths is still under study.
NOTE 7 – The link fails to meet the error performance requirement if any of the objectives is not
met.
NOTE 8 – In the context of this Recommendation, the link consists in section(s) and/or path(s).
NOTE 9 – In the case of multihop links the objectives derived according to this Recommendation
apply to the overall links (irrespective of the date when each hop was brought into service and of
the number of independent operators involved); the allocation of the objectives to each hop is under
the responsibility of the relevant network operators.
NOTE 10 – Annexes 1, 2 and 3 may be used for additional guidance in the application of this
Recommendation.
ANNEX 1
Examples of calculations of the error performance
parameters ESR, SESR and BBER
This Annex shows some examples of the application of this Recommendation to real links, in order
to derive the objectives.
The calculations are made for ESR, SESR and BBER for a link length, Llink, of 105 km.
Furthermore:
An intermediate country is assumed.
BR is assumed to be equal to 1.
The evaluation time is one month (30 days).
Rec. ITU-R F.1397-2
5
Example 1:
Bit rate: 150 336 kbit/s (VC-4, TC-4), i.e. objectives according to ITU-T Recommendation G.828.
The objectives are calculated from equation (1) and with B1 and C1 from Table 1a.
ESR  2  10–3 (1  1)  105/2 500  0  168  10–6
Number of ES/month  435
SESR  1  10–4 (1  1)  105/2 500  0  84  10–7
Number of SES/month  22
BBER  5  10–6 (1  1)  105/2 500  0  4.2  10–7
Number of BBE/month  8 709
Example 2:
Bit rate: 140 Mbit/s, i.e. objectives according to ITU-T Recommendation G.826.
The objectives are calculated from equation (1) and with B1 and C1 from Table 2a.
ESR  8  10–3 (1  1)  105/2 500  0  672  10–6
Number of Es/month  1 741
SESR  1  10–4 (1  1)  105/2 500  0  84  10–7
Number of SES/month  22
BBER  1  10–5 (1  1)  105/2 500  0  8.4  10–7
Number of BBE/month  17 418
ANNEX 2
Example of a path, link, hop
This Annex clarifies the meaning of some terms related to the connection, used in the body of the
Recommendation.
The definition of path is given in ITU-T Recommendation G.826; an example of a radio link
forming a portion of a path is given in Fig. 1.
FIGURE 1
Example of a portion of path
Path end point (PEP)
PEP
Path
Link 1
(e.g. fibre optics)
Link m
(e.g. radio)
Link n
(e.g. fibre optics)
Real radio link
Hop 1
Hop 2
Hop w
1397-01
6
Rec. ITU-R F.1397-2
ANNEX 3
Relationship between BER and EB
In order to find the relationship between BER (ITU-T Recommendation G.821) and the percentage
of EB (ITU-T Recommendation G.826), some measurements have been carried out on several
digital radio-relay systems, with different modulation codes.
The results, obtained in the laboratory by setting the BER value by means of a variable attenuator
on a simulated hop are reported in Fig. 2, showing on the horizontal axis the BER and on the
vertical axis the percentage of EB.
FIGURE 2
Relationship between BER and EB
140 Mbit/s
100
90
80
70
EB (%)
60
50
40
30
20
10
0
10–2
10–3
10–4
10–5
10–6
10–7
BER
Gaussian
16-QAM no forward error correction
16-QAM
16-BCM
64-QAM
128-TCM
BCM: block code modulation.
1397-02
Rec. ITU-R F.1397-2
7
Figure 2 gives the percentage of EB related to each BER value for each system, in particular it is
possible to read which value of BER corresponds to the ITU-T Recommendation G.826 SES
threshold (30% EB).
As far as the SES parameter is concerned, the design of radio links according to this
Recommendation (and according to ITU-T Recommendation G.826) could be made by following
the usual methods adopted up to now, provided that the value of BER corresponding to 30% EB is
used instead of the 1  10–3 BER value that was used for design of links according to
ITU-T Recommendation G.821.